refactor(scripts): parameterize hostnames in deployment scripts

- setup-host.sh: add SILO_DB_HOST and SILO_MINIO_HOST env var
  overrides, update Go version from 1.23 to 1.24, expand generated
  silod.env template with session secret and admin password fields
- deploy.sh: add SILO_DEPLOY_TARGET and SILO_DB_HOST env var
  overrides for target host and database host
- setup-ipa-nginx.sh: replace hardcoded hostname with SILO_HOSTNAME
  env var (default: silo.example.internal), parameterize SILO_PORT,
  use variable substitution in nginx config template

All scripts retain backward-compatible defaults.

scripts/deploy.sh

@@ -1,18 +1,23 @@
 #!/bin/bash
-# Deploy Silo to silo.example.internal
+# Deploy Silo to a target host
 #
 # Usage: ./scripts/deploy.sh [host]
-#   host defaults to silo.example.internal
+#   host defaults to SILO_DEPLOY_TARGET env var, or silo.example.internal
 #
 # Prerequisites:
 #   - SSH access to the target host
 #   - /etc/silo/silod.env must exist on target with credentials filled in
-#   - PostgreSQL reachable from target at psql.example.internal
-#   - MinIO reachable from target at minio.example.internal
+#   - PostgreSQL reachable from target (set SILO_DB_HOST to override)
+#   - MinIO reachable from target (set SILO_MINIO_HOST to override)
+#
+# Environment variables:
+#   SILO_DEPLOY_TARGET  - target host (default: silo.example.internal)
+#   SILO_DB_HOST        - PostgreSQL host (default: psql.example.internal)
 
 set -euo pipefail
 
-TARGET="${1:-silo.example.internal}"
+TARGET="${1:-${SILO_DEPLOY_TARGET:-silo.example.internal}}"
+DB_HOST="${SILO_DB_HOST:-psql.example.internal}"
 DEPLOY_DIR="/opt/silo"
 CONFIG_DIR="/etc/silo"
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
@@ -104,7 +109,7 @@ echo "  Files installed to $DEPLOY_DIR"
 REMOTE
 
 echo "[6/6] Running migrations and starting service..."
-ssh "$TARGET" bash -s <<'REMOTE'
+ssh "$TARGET" DB_HOST="$DB_HOST" bash -s <<'REMOTE'
 set -euo pipefail
 
 DEPLOY_DIR="/opt/silo"
@@ -123,14 +128,14 @@ if command -v psql &>/dev/null && [ -n "${SILO_DB_PASSWORD:-}" ]; then
     for f in "$DEPLOY_DIR/migrations/"*.sql; do
         echo "    $(basename "$f")"
         PGPASSWORD="$SILO_DB_PASSWORD" psql \
-            -h psql.example.internal -p 5432 \
+            -h "$DB_HOST" -p 5432 \
             -U silo -d silo \
             -f "$f" -q 2>&1 | grep -v "already exists" || true
     done
     echo "  Migrations complete."
 else
     echo "  WARNING: psql not available or SILO_DB_PASSWORD not set, skipping migrations."
-    echo "  Run migrations manually: PGPASSWORD=... psql -h psql.example.internal -U silo -d silo -f /opt/silo/migrations/NNN_name.sql"
+    echo "  Run migrations manually: PGPASSWORD=... psql -h $DB_HOST -U silo -d silo -f /opt/silo/migrations/NNN_name.sql"
 fi
 
 # Start service